The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
With the development of wireless network techniques, various 802.11x standards are continuously updated, and new wireless network architectures and techniques are continuously proposed. One new network is a wireless mesh network. The wireless mesh network may be referred to as a “multi-hop” network, which is a new wireless network technique that differs significantly from the conventional wireless network. In a conventional wireless local-area network, since each client accesses the network via a wireless link connected with an Access Point (AP) of the wireless local-area network. Communications between subscribers must be performed via APs. Such a network and supporting architecture is called an infrastructure wireless network. However, in the wireless mesh network, each wireless device node can concurrently serve as an AP and a router. Each node can transmit and receive data and directly communicate with one or more peer nodes. This combines the advantages of the conventional Wireless Local-area Network (WLAN) and that of the Ad-hoc network to provide a wireless network with a high data rate and a wide coverage area.
FIG. 1 is a schematic diagram illustrating the topology structure of the WLAN in the prior art. Each Access Point (AP) of the WLAN has only one physical interface (PHY), and the AP is connected with an HTTP server, device nodes (STAs) in other local area networks, and other local area networks, etc. in a wired manner. The connections with other LANs are implemented via wired, distributed systems. Each AP accessing the WLAN is connected with the respective mobile nodes via different channels of its physical interface (PHY) by adopting existing wireless connections, such as using 802.11 standard. Different APs use different channels, such as the channels CH1 and CH5 as shown in FIG. 1. In FIG. 1, the DS Links are denoted by thick solid lines, the conventional 802.11 BSS Link wireless connections are denoted by dashed lines, and the conventional 802.x Link wired connections are denoted by thin solid lines.
Compared with the conventional switch network, the wireless mesh network is a new network architecture based on multi-hop routing and peer-to-peer network techniques, with the characteristic of mobile wide band. The wireless mesh network can be dynamically and continuously extended. In addition, the wireless mesh network has characteristics of self-organizing, self-managing, and self-healing. The wireless mesh network also has the redundancy mechanism and multi-path routing functions provided by the distributed network. In the wireless mesh network, the nodes can automatically join or move out of the network. The network can automatically discover the changes of network topology structure and compute another optimal multi-hop routing according to the changes. Therefore, the routing technique becomes a critical technique in the mesh network.
The Simple Efficient Extensible Mesh (SEE-Mesh) network provides a hybrid routing protocol for the wireless mesh network (HWMP, Hybrid Wireless Mesh Protocol), which combines the advantages of on-demand routing and proactive routing to provide flexible routing service for nodes in the mesh network. The routing protocol is based on the Ad-hoc on-demand routing Ad-hoc On-demand Distance Vector (AODV) and the tree-based proactive routing Tree-Based Routing Protocol (TBRP).
According to the routing protocol, if no Mesh Access Point (MAP) has a gateway (portal) to connect with an external network, all the nodes in the mesh network determine data transmission paths via the AODV routing protocol.
When an STA needs to transmit data, a path query message based on the on-demand routing is broadcasted immediately. The request is sent to a destination STA by multi-hop broadcasting of neighbor nodes. The destination STA selects an optimal route to send a response to the source STA. In this case, a data transmission link is established. The source STA sends a path query request message at a regular time interval to maintain the dynamically established routing path until the data transmission is finished.
If a Mesh Access Point MAP has a gateway (portal) to connect with an external network, the MAP can be determined as the “root” of a Tree-based routing protocol. The “root” node MAP maintains a routing tree according to the proactive routing algorithm, and each of the other nodes gets its parent node via the AODV routing protocol and maintains a routing path to the “root” node MAP. When an STA needs to transmit data, the data is first transmitted to the “root” node MAP via the proactive Tree-based routing protocol, and the “root” node MAP forwards the data to the destination STA according to its maintained routing table, and then the destination node continues the data transmission via the routing path to the source node for subsequent data transmission.
If the mesh network has no gateway (portal) for communication with an external network, the routing protocol completely depends on the on-demand routing mechanism of AODV (Ad-hoc On-demand Protocol). However, the AODV is dedicatedly designed for the Ad-hoc network and not optimized for the characteristics of the mesh network, and the path query messages of AODV will lead to a broadcast storm in the whole mesh network so that substantive network band-width may be occupied. Therefore, the operating efficiency of the routing protocol in the mesh network is low.
Also, because of the network broadcast storm, the routing protocol can not meet the requirements of multiple Quality of Service (QoS). Further, since a significant portion of the of broadcast storm for the AODV routing protocol occurs during the routing request, the increase of the number of nodes in the mesh network is limited, which therefore reduces the extensibility of the mesh network.
Since AODV is based on on-demand routing, the protocol has to maintain every link for data transmission. Since the rapid movement of nodes results in frequent handover between the wireless mesh access points (MAPs), the maintenance results in a large overhead and a long delay for data transmission, thereby making the protocol not be well adapted to rapid MAP handover.
If the Tree-based Proactive Routing Protocol is applied, the “root” node MAP is responsible for the establishment and maintenance of the routing trees in the whole network, which brings the problems of bottleneck and single-point failure. Therefore, the implementing method and operation process for the hybrid routing protocol are very complex, which affects the simplicity and convenience of the routing protocol in the mesh network.